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Determining the storage, availability and reactivity of NH3 within Cu-Chabazite-based Ammonia Selective Catalytic Reduction systems

Abstract

Three different types of NH3 species can be simultaneously present on Cu2+-exchanged CHA-type zeolites, commonly used in Ammonia Selective Catalytic Reduction (NH3-SCR) systems. These include ammonium ions (NH4+), formed on the Brønsted acid sites, [Cu(NH3)4]2+ complexes, resulting from NH3 coordination with the Cu2+ Lewis sites, and NH3 adsorbed on extra-framework Al (EFAl) species, in contrast to the only two reacting NH3 species recently reported on Cu-SSZ-13 zeolite. The NH4+ ions react very slowly in comparison to NH3 coordinated to Cu2+ ions and are likely to contribute little to the standard NH3-SCR process, with the Brønsted groups acting primarily as NH3 storage sites. The availability/reactivity of NH4+ ions can be however, notably improved by submitting the zeolite to repeated exchanges with Cu2+, accompanied by a remarkable enhancement in the low temperature activity. Moreover, the presence of EFAl species could also have a positive influence on the reaction rate of the available NH4+ ions. These results have important implications for NH3 storage and availability in Cu-Chabazite-based NH3-SCR systems.

Category

Academic article

Language

English

Author(s)

  • Inés Lezcano-González
  • Upakul Deka
  • Bjørnar Arstad
  • Andy Van Yperen-De Deyne
  • Karen Hemelsoet
  • Michel Waroquier
  • Véronique Van Speybroeck
  • Bert M. Weckhuysen
  • Andrew M. Beale

Affiliation

  • Utrecht University
  • M2I - Materials innovation institute
  • SINTEF Industry / Process Technology
  • Ghent University

Year

2014

Published in

Physical Chemistry, Chemical Physics - PCCP

ISSN

1463-9076

Publisher

Royal Society of Chemistry (RSC)

Volume

16

Issue

4

Page(s)

1639 - 1650

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